Charge pumps or voltage multipliers are generally known in the art of integrated circuit design and have been used for high voltage generation for various applications, such as EEPROMs, flash memories and DC bias voltage generation for condenser microphones. In integrated circuit designs of today, the charge pump is typically operated from a set of non-overlapping clock signals.
An intrinsic disadvantage of prior art charge pumps used for biasing of condenser microphones such as MEMS/silicon condenser microphones is a large ramp-up time of the DC output voltage from the charge pump. The large ramp-up time is caused by high source impedance associated with the charge pump and large capacitive loads at the output of the charge pump. A large portion of the capacitive load is often associated with the capacitance of the capacitive electro-acoustic transducer element.
An object of embodiments of the present invention is to provide a charge pump for biasing condenser microphones. The charge pump has a reduced ramp-up time of the charge pump DC output voltage compared to prior art charge pumps.
Another object of embodiments of the present invention is to provide a charge pump facilitating accurate setting of the DC output voltage to a desired voltage.